1. Field of the Invention
The present invention relates to zippers and more particularly, to a double sided nylon sandwich mesh fabric zipper and slider assembly in which the coil strips are left handed and right handed plastic coils each having a center cord and a series of interlocking teeth, each tooth having a tooth head and a tooth body so configured that the tooth heads of the teeth of the coil strips at one zipper tape are respectively interlockable with the tooth heads of the teeth of the coil strips at the other zipper tape; the slider has C-shaped guide grooves defined in upper and lower chambers therein to guide horizontal movement of the teeth of the upper and lower coil strips smoothly between locking and unlocking positions, and a balance guide block protruded from the central partition plate thereof and configured to match with the configuration of the tooth heads of the interlocking teeth of the coil strips, facilitating accurate alignment between the left and right teeth of the upper and lower coil strips and assuring smooth engagement and disengagement of the interlocking teeth.
2. Description of the Related Art
Nylon zippers are intensively used in garments, cases, bags and many other accessories. Following increasing in economic activity and competition, users need more about zipper's applicability and special functions. Conventional zipper designs can no longer satisfy clients' requirements and expectation, such as: strength enhancement, prevention of malengagement, waterproof feature, anti-bacteria, safety enhancement, environmental protection, and etc. Conventional nylon zippers are commonly of single side design, comprising two zipper tapes, and two series of interlocking teeth respectively fastened to the respective top walls of the zipper tapes with stitches. Further, Taiwan Patent Number 441257 & China Patent Number ZL00233580.8 discloses a nylon zipper structure, entitled “Improvement of nylon zipper tape” (see FIGS. 1˜3). According to this design, each lateral side 701 of the center cord 70 of each coil strip is kept away from the tooth head 711 of the associating series of interlocking teeth 71 (see FIG. 3). Thus, when fastening the coil strips to the zipper tapes all together, the stitching action of the needle may stitch the interlocking teeth, causing stitching problems. To avoid this problem, each coil strip 7 is separately stitched to one respective zipper tape 8, and then the two zipper tapes 8 with the respective stitched coil strips 7 are fastened together. However, this method is complicated. Further, because the two coil strips 7 are respectively and separately stitched to the respective zipper tapes 8, the stitch seams that secure the respective coil strips to the respective zipper tapes may be not kept perfectly in parallel, in consequence, the teeth of the two coil strips may be not accurately aligned for smooth engagement and disengagement. Further, as the teeth of the two coil strips are not accurately aligned, the H-shaped guide grooves 91 in the upper and lower chambers inside the slider 9 may be unable to guide the teeth of the two coil strips into positive engagement, leading to protruding teeth and malengagement. This problem will be more serious when the slider is being moved to a turning corner area.